Recent developments of high-brightness light emitting diodes (LED) have opened new horizons in lighting. Highly efficient and reliable LED lighting continuously wins recognition in various areas of general lighting, especially in areas where cost of maintenance is a concern. LEDs are being adopted in a wide variety of electronics applications, for example, architectural lighting, automotive head and tail lights, backlights for liquid crystal display devices including personal computers and high definition TVs, flashlights, etc. Compared to conventional lighting sources such as incandescent lamps and fluorescent lamps, LEDs have significant advantages, including high efficiency, good directionality, color stability, high reliability, long life time, small size, and environmental safety
Referring to FIG. 1, a prior art LED driver 10 of a boost type is shown. The LED driver 10 may have a positive input voltage source +VIN, an input filter capacitor 110, a boost inductor 111, a controlled switch 113, a rectifier diode 112, and an output capacitor 114. In the embodiment shown in FIG. 1, the LED driver 10 may be coupled to a positive input voltage source +VIN. The input filter capacitor 110 may have a first terminal coupled to the positive input voltage source +VIN and a second terminal coupled to ground. The boost inductor 111 may have a first terminal coupled to the positive input voltage source +VIN and the first terminal of the input filter capacitor 110. A controlled switch 113 may have a first terminal coupled to the second terminal of the boost inductor 111, a second terminal for receiving a control signal, and a third terminal coupled to ground. The rectifier diode 112 may have a first terminal coupled to the first terminal of the controlled switch 112 and the second terminal of the boost inductor 111. The output capacitor 114 has a first terminal coupled to a second terminal of the rectifier diode 112 and to a first terminal of the LED load 200 and a second terminal coupled to ground. The load switch has a first terminal coupled to the second terminal of the LED load 200, a second terminal coupled to a control signal, and a third terminal coupled to ground. While the above LED driver 10 does function, the LED driver 10 has a limitation of the LED load 200 not been wired to ground directly, which is required for many applications.
Therefore, it would be desirable to provide a circuit and method that overcome the above problem.